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I'm about to get my roof replaced and while that is happening I am trying to correct some very outdated attic ventilation design. For context, I am in Southern Arizona so primarily hot & dry.

My current attic has gable vents at one end. Once upon a time it had a gable vent at the other end, but a carport was added at some point that effectively blocks that gable end (especially since I have since converted the carport to an insulated garage).

There are two passive turbine vents near the ridge. They are both totally worn out.

My roofer has suggested adding ridge vent, which I think is a good idea. I have soffit venting at the front of the house, but the back soffit vents were blocked by an addition.

My questions:

  • Can I remove the gable vents if I have the ridge vent?
  • Should I think about adding an active (solar or wired) attic vent to maximize attic cooling in the summer?
  • Is it a major issue to have the rear soffit vents blocked? In theory this could be rectified but it would be major surgery.

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Attic ventilation requires inputs and outputs, just like most systems in life. With only one gable vent and even with ridge vents you're effectively only scavenging a narrow path between the two. Very little mixing occurs outside this stream. The outer reaches of your attic and the end opposite the gable vent will be virtually stagnant, and therefore hotter than blazes.

Yes, it's a problem that your soffit vents are inoperative. No, you should not close the gable vent if you have no other inputs. Yes, if you can't get a comprehensive passive system restored into service you should install an active system, but this must include circulation to the areas mentioned above as currently unhandled.

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  • Makes sense, thank you! I'm guessing that no matter what, adding an active system can't hurt (given that where I am it's typically hot & dry).
    – icurays1
    Jan 24 at 18:07
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    That's not a logical assumption. Active systems have initial and ongoing costs. If they aren't offset by the energy savings inside the home they can hurt.
    – isherwood
    Jan 24 at 18:10
  • Fair. I'll let the roofers do their ridge vent, I'll keep the gable vent for now and try to even add one on the opposite end where it's blocked (there is just enough roof that I should be able to get in a couple small ones). Then, when it starts to heat up, I'll see how my attic is doing and decide if I need to go further.
    – icurays1
    Jan 24 at 18:13
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    That's not a bad initial strategy, but it's common knowledge among builder types that gable and ridge venting creates a short-circuit that leaves the outer portions of the attic unventilated. Soffit vents are almost a modern requirement.
    – isherwood
    Jan 24 at 18:15
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    Understood. I'll have to strategize how to deal w/ the blocked rear soffit vent down the road though. Whoever did the addition wasn't thinking straight - the addition has unvented vaulted ceilings that block the vents on the backside of the old roof. Short of gutting the ceiling in the addition I don't know how else it could be rectified. May need to go that route eventually but will see how it goes for now.
    – icurays1
    Jan 24 at 18:18

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